Field of the Invention
The present invention relates to a rotating body provided with a plurality of blades, such as a turbine rotor for a gas turbine engine or a steam turbine, and more particularly to an arrangement structure of the blades in the rotating body.
Description of Related Art
A rotating body for use in turbomachinery such as a gas turbine engine or a jet engine rotates at a high speed, with a large number of turbine rotor blades being arranged at equal intervals on an outer circumferential portion of a rotor. When the multiple rotor blades are manufactured, occurrence of variations (mistuning) in mass, rigidity, and natural frequency among the rotor blades is unavoidable. Depending on the arrangement of the rotor blades, critical vibration may occur in the rotor blades due to influence of resonance caused by such mistuning. In addition, the mistuning may cause resonance at a vibration frequency or in a vibration mode, which are outside a design plan. Such vibration may cause a reduction in the life of the blades.
In order to suppress the vibration due to the variation in mass of the rotor blades, there have been proposed, for example, a method in which an amount of unbalance around a rotation axis is adjusted by arranging rotor blades at opposed diagonal positions on the circumference of a rotor, successively in order from a rotor blade having a larger mass (e.g., Patent Document 1), and a method in which rotor blades are arranged on the basis of natural frequencies measured for the respective rotor blades (e.g., Patent Document 2).